[Bug target/26778] GCC4 moves the result of a conditional block through inadequate registers

[guillaume dot melquiond at ens-lyon dot fr]

------- Comment #3 from guillaume dot melquiond at ens-lyon dot fr  2006-04-05 08:59 -------
Since the runtime slowdown between the binaries produced by GCC3 and GCC4 was
not negligible, I did search a bit more for workarounds. It was quite simple in
fact: passing -mno-sse produced assembly code roughly as efficient. With
-mno-sse, the testcase obviously does not use any xmm register anymore. But in
addition it does not use any callee-save register anymore, and hence it uses
less stack space and prologue and epilogue are shorter. As a consequence, the
generated code is both faster and shorter with -mno-sse. In fact, the testcase
binary is even 30% shorter than if it had been produced with -Os. (The same
binary is generated for both -O3 and -Os.)


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26778